During osteoblast differentiation, transcription activation of the osteocalcin gene is accompanied by the presence of two nuclease- hypersensitive sites in the promoter region of this gene, both representing key transcriptional regulatory elements. AML gene products have been known to play a role in regulating basal and tissue specific expression of osteocalcin gene in bone cells. In the current research proposal, the investigators will examine the role of transcription regulatory elements including the three AML binding sites in modeling the chromatin organization. Specific aim one is designed to determine the regulatory parameters that mediate the chromatin structure of the bone specific osteocalcin gene locus in osteoblasts. In specific aim two, the investigators will analyze biochemical and molecular mechanisms that alter the chromatin structure of the promoter of the osteoblast- specific gene osteocalcin. For both of these specific aims, the chromatin structure of the rat osteocalcin (OC) promoter will be assayed by using DNase I hypersensitivity, micrococcal nuclease digestion, restriction endonucleases digestion, genomic footprinting in intact cells and gel shift assays.